1. Field of the Invention
The present disclosure relates to a method and a system for recognizing a location by using an ultrasonic signal, more particularly, to a method and a system for recognizing a location which are capable of calculating a coordinate of a moving object by using a plurality of ultrasonic satellites generating ultrasonic signals simultaneously.
This work was supported by the IT R&D program of MIC/IITA [Work Management Number: 2007-S-108-01, The Development of u-Experience content operating platform based on mixed reality]
2. Description of the Related Art
In recent years, a Global Positioning System (GPS) is widely used as one of the systems for recognizing a location, and is provided in a wide area by using an outdoor artificial satellite. However, the location recognizing system using such a GPS cannot be used in an indoor environment, and may not be inoperable in an area crowded with buildings. Furthermore, the location recognizing system using such a GPS has good relative accuracy in a very wide area, but has a repeatable accuracy as low as several meters in a small area.
Korean Patent No. 0351962 entitled “Navigation System Using Pseudolites” discloses a method that can be also used indoors by complementing typical systems for recognizing a location. However, such a system has a difficulty in being practically used because signal strength thereof is greatly changed in a close range.
Therefore, various techniques have been proposed to apply ultrasonic signals to the system for recognizing a location in easier way than the above systems.
FIG. 1 is a schematic view illustrating the Bat ultrasonic location system proposed as an active Bat system by AT&T Laboratories Cambridge. The system has the characteristic of transmitting ultrasonic signals from a moving object. The method for recognizing a location by using the ultrasonic signals is a method for calculating an arrival time of an ultrasonic signals transmitted from the moving object at a number of receivers because the moving object has a difficulty in transmitting a number of ultrasonic signals simultaneously due to interference property of the ultrasonic signals differently from a method using a radio wave. However, there is a disadvantage in that such a method is applicable to only a single moving object.
U.S. Pat. No. 5,793,704 entitled “Method and Device for Ultrasonic Ranging” discloses method for calculating a distance by using the maximum amplitude of an ultrasonic signal, but this method has a complex configuration and a limitation in its performance.
Korean Patent Publication No. 10-2003-0093387 entitled “Ultrasonic Sensor System for Position and Direction Estimation of Mobile Object” discloses a method for allowing a moving object to receive ultrasonic signals. However, a number of moving objects cannot be independently operated in this system because synchronizing signals are transmitted from the moving object. This system requires another regulation due to interference between ultrasonic signals transmitted from a number of moving objects.
Korean Patent Application No. 10-2005-0018538 entitled “Positioning System Using Ultrasonic and Control Method of the System” employs a method for measuring a distance from each of transmitters by fixing ultrasonic transmitters and sequentially transmitting ultrasonic signals. However, a measurement of a location of a moving object may be delayed according to the number of ultrasonic satellites necessary for recognizing transmission interval and transmission location of ultrasonic signals because all ultrasonic transmitters must transmit ultrasonic signals by once in order to calculate a location of a receiver.